I know it's kind of a newb question. I've been unable to figure it out or find anything about it on the stickies, please direct me to one if I missed it somewhere.

How does the steering mechanism connect to the axles and where exactly are the wheel bearings located? How do the CV joints work?

How exactly do the control arms play a role in steering and/or suspension?

The reason I ask is because I may need to replace both of my front outer CV joints and I want to replace as many worn-out suspension/driveline components as possible so I won't have to worry about them in the future.

I know both CV joints are included in a driveaxle assembly, but what about wheel bearing? If I need to replace a CV joint, why shouldn't I just replace the whole axle?

 

They don't. The steering rack connects to the hub assemblies through the tie rods. The axles enter the hub assemblies separately. The CV joints are meshing gears that allow the hubs to turn while still remaining meshed to drive the wheels. The wheel bearings are inside the hub assemblies, and let the rotating parts of the hub spin while you drive.

The control arms are basically sprung locating mounts for the hub. They help support the car with respect to the hubs and wheels. Body motion (and the damping of that motion) are controlled by the springs and shocks. With respect to steering, the control arms are mounted on pivoting mounts to the body and hub. Different-length arms have a different pivoting radius. If you have a lower arm that is longer than an upper arm, and the suspension compresses (say, when you're in a left hand turn), it'll "pull" the top of the wheel in. Without this motion, if the wheel had equal-length upper and lower control arms, when you turned, the wheel would remain vertical with respect to the body, and the whole thing would roll over onto the outer edge of the tire. Because a shorter upper arm pivots more "tightly", it pulls the top of the tire inward (creating negative camber), and that keeps the tread more or less flat on the ground.

If you have to replace the CV joint, you may as well just replace the whole axle. It's easier, less labor intensive, and not much more money. I bought two front drive axles for my A4 for $99.95 each from www.germanautoparts.com and they're great. With the A4, control arm failure is expected - you can get entire replacement kits online (for every control arm on the car) for anywhere from about $300-500, depending on where you buy them. The wheel bearing replacement is separate from the axle replacement, and unless the shop (or you) can use a HubShark (on-the-car press), the spindle (hub) has to come off the car to press out the bearing and press in the new one. Wheel bearing failure is also common on our cars.

 

Just the answers I was looking for. Thanks!

 

No problem